Prosthetic heart valves are used to replace damaged or diseased heart valves. The natural heart valves are the aortic, mitral (or bicuspid), tricuspid and pulmonary valves. Prosthetic heart valves can be used to replace any of these naturally occurring valves. Repair or replacement of the aortic or mitral valves is most common because they reside in the left side of the heart where pressures are the greatest.
Where replacement of a heart valve is indicated, the dysfunctional valve is typically cut out and replaced with either a mechanical valve or a tissue valve. Typically, an artificial valve has flexible (e.g., bioprosthetic) leaflets attached to a wireform structure with arcuate cusps and upstanding commissures supporting the leaflets within the valve. The artificial valve also has an annular stent and a soft sewing ring for better attachment to and sealing against the native valve annulus. The alternating cusps and commissures mimic the natural contour of leaflet attachment. Importantly, the wireform provides continuous support for each leaflet along the cusp region so as to better simulate the natural support structure.
In a typical prosthetic heart valve implantation, approximately 12-18 sutures are placed through the patient's native valve annulus. These sutures are subsequently passed through the sewing ring of the prosthetic valve outside of the surgical cavity. The valve is then “parachuted” down these sutures to the point where it meets the target annulus. At that point, the sutures are tied to secure the prosthesis to the heart. The process of placing the sutures through the annulus and subsequently tying 3-10 knots per suture is very time consuming and greatly adds to the time the patient is on heart-lung bypass, anesthesia, etc. There is a direct correlation between time spent on heart-lung bypass and poor outcomes. Additionally, for mitral valves, there is the possibility of “suture looping” to occur during knot tying in which the suture is looped over a valve commissure and partially constrains a pair of valve leaflets, thus preventing normal function of the prosthesis.
Various methods of attaching a prosthetic heart valve to a heart with few or no sutures have been developed in the past. Attempted attachment methods include the utilization of hooks or barbs integrated into the prosthesis that bite into the native tissue to anchor the device. These devices have bulky delivery systems and it can be difficult to position the prosthesis accurately.
Another possible solution is to implant a valve in much the same way as traditionally done with sutures, but to replace most or all of the sutures with rapidly deploying clips to attach the sewing ring to the annulus. Past designs have disclosed instrumentation that would deploy a clip with sharpened edges necessary to puncture the tissues or materials that are to be secured together. Such designs with sharp-ended clips have created local tissue irritation due to the exposed ends.
Most of the current devices, such as those disclosed in U.S. Pat. Nos. 5,480,406; 6,913,607; 7,407,505; and 7,862,572 all require access to both sides of the tissue/structures which are being sewn/clipped together. This is of particular disadvantage in attaching a prosthetic heart valve to an annulus because the prosthetic valve impedes access to the inflow side of the annulus.
It would therefore be desirable to develop a method of attaching a prosthetic heart valve to a valve annulus with few or no sutures, using a smaller device to deliver the clips which requires access to only one side of the target. It would also be advantageous to have a deployment mechanism with a clip with no sharp edges or tips so as to reduce tissue irritation.